Primers

[Kensal Rise]

As you've seen, primer selection and cartridge loads can effect the function of many old doubles. So can firing pin tip condition. If they've been roughed up by corrosive priming in the past, they can stick. The action's cocking speed is also a consideration. Because of the design of the Parker's action, it can pull the tumblers back to cocked position a bit slower than other designs. (For more details, please see my new book, Birth of The Boxlock) It can all add up.

[Cold Spring]

Originally Posted by Chris Pope

So I hope I am not inappropriately changing the topic but...being new to the Parker world...here's my follow up question...if you have to fight a bit to open the action after firing a round isn't that doing harm to the Parker?
The reason I ask...after purchasing my first Parker a couple years ago I took it to SD to work on some pheasants. I ran out of my handloads (which were loaded to a spec recommended on a discussion board here) and substituted a factory ammo (now can't remember brand or data) and started having to exert a little bit of pressure to open the action. I stopped using the factory ammo because I thought it might be harming the shotgun. Is that a legitimate concern for these Parkers?

Chris, in answer I'd say you're not doing your Parker or any other vintage double-gun any good by forcing it open due to using contrary primers or shells. Your hand pressure puts a "bending moment" as in Mech Engineering/Physics on the barrels and if you've got a barrel rib(s) with weak solder attachment that could cause it to further loosen or pop.